Tissues Chapter 5 p.144-147 Cytology: study of the structure and function of the cells

Histology: study of the composition and function of tissues *Cells donʼt work alone, they work together by forming tissues.

4 Main tissue groups: Epithelial, Muscular, Nervous, Connective " -cells within these tissue groups differ in size, shape, arrangement, " " function, and location. -“Stem cells” are specialized cells that can give rise to many cell types. They have the ability to divide into adulthood and give the body a sort of built-in repair mechanism. Important in liver and nerve cell damage. These cells divide a number of times and thatʼs it, they are alive but, donʼt divide. However, if these areas are damaged then the stem cells can produce new cells.

*Epithelial Tissues* - differ by number of layers and shape

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number of layers----> (simple) = single layer (stratified) = two or more layers of cells

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shape----> (squamous) = thin, flattened (cuboidal) = cube-like " (columnar) = elongated

*epithelial tissues donʼt have blood vessels " -easily divide " -include skin, lining of stomach, intestines, mouth, and cells covering " " organs

Simple Squamous Epithelium - single layer of thin, flattened cells - line air sacs of lungs - walls of capillaries - inside of blood vessels and lymph vessels - make-up the membranes that line the body cavities - allow substances to pass easily through because so thin, but easily " damaged

Simple Cuboidal Epithelium - single layer of cube-shaped cells - covers ovaries - lines kidney tubules, ducts of some glands (salivary gland, pancreas, " "liver) " " " - function to secrete and absorb substances

Simple Columnar Epithelium - single layer of elongated cells - line trachea - female reproductive tubes with cilia, helps move egg to uterus - line uterus (these are non ciliated; no cilia, no movement) and part of " digestive tract (stomach, large/small intestines) - because they are elongated, theyʼre relatively thick tissue and protect " underlying tissues - can secrete digestive fluids and absorb nutrients

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-----> Pseudostratified Columnar Epithelium " - appear stratified (layers of cells) but are not really, they look " layered because nuclei are at different levels. " - have cilia and secrete mucus (helps trap dust and move it " out) " - this epithelium lines respiratory system passages

Stratified Squamous Epithelium - many layers of flattened cells (so thick) - cells more flattened near the surface, where deeper cells are cuboidal or " columnar in shape because they are actively dividing - found in outermost layer of skin (epidermis)- so first line of defense - a protein found in keratin accumulates in the older cells which harden " and die. These make the skin dry, tough and waterproof, it also doesnʼt " allow organisms or chemicals to enter. - in lining of oral cavity, throat, vagina, and anal canal- no keratin is " produced here so tissues remain soft and moist.

Stratified Cuboidal Epithelium - made up of two to three layers of cube-shaped cells which forms the " lining of a lumen (space within a tubular structure) like a blood vessel or " intestine - lines the ducts of the mammary glands, sweat glands, salivary glands, " pancreas, and lining of the male and female reproductive system (ovarian " follicles and seminiferous tubules).

Stratified Columnar Epithelium - several layers of cells, the top (superficial) cells are elongated, with the " lower layers being more cube-shaped. - in the vas deferens (male reproductive tract) and pharynx - looks similar to pseudostratified columnar, but all the cells donʼt reach "and touch the basement membrane.

- Transitional Epithelium - specialized cells which change in response to tension - allow an area to expand - urinary bladder and lining of ureters and urethra - when these areas are contracting the tissue consists of many layers of "" cuboidal cells (unstretched) - when these areas are distended (stretched) the physical appearance of " the cells change and the tissue appears thinner, (p. 147, fig. 5.9), this " change also prevents urine from diffusing back into the internal " environment by acting like a barrier of sorts. Glandular Epithelium - specialized cells which produce and secrete substances into ducts or " into body fluids. " *exocrine gland- glands which secrete products into a duct " *endocrine gland- glands which secrete into tissue fluid or blood

Exocrine glands can consist of single cell layers or be multicellular; multicellular types are subdivided into simple or compound types Simple" " " - simple tubular" " " - simple branched tubular" - simple coiled tubular - simple branched alveolar"

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" Compound - compound tubular - compound alveolar

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(see fig. 5.10, p. 149)

Exocrine glands are also classified by the way they secrete their products Merocrine- release secretions without losing cytoplasm Apocrine- lose some parts of their cell bodies when secreted Holocrine- release entire cells with secretory substances

Ex. Merocrine ----> salivary, pancreatic, sweat glands Apocrine ----> mammary glands, glands lining ear canal Holocrine ----> sebaceous glands of skin associated with hair follicle " " (oil / pimples)

*Connective Tissues* - most abundant tissue type by weight - bind structures, provide support and protection, form framework, fill " "spaces, store fat, produce blood cells, protect against infection, and help " "repair tissues - connective tissues cells arenʼt always directly next to each other like " epithelial cells, but have a lot of a cellular material (matrix) between them *Connective tissues also contain different cell types - fibroblasts = large, star-shaped cells which produce 3 types of " " " " " connective tissue fiber " " " " 1. collagenous fiber " " " " 2. elastic fiber" " ( see below ) " " " " 3. reticular fiber - mast cells= large cells located near blood vessels " - release “heparin” which prevents blood clotting " - also release “histamine” which is involved with inflammatory " responses and allergies (asthma / hay fever) - macrophages " - start as WBC " - attach to fibers but can detach and move around " - specialized to carry on phagocytosis, helping remove foreign " " invaders to the bodyʼs tissues (so important in immunity)

*Both fibroblasts and mast cells are considered fixed cells because they are formed in certain areas in stable numbers.

*Macrophages are considered wandering cells because they move about and appear in tissues which are injured or infected.

1. Collagenous fibers- thick threads of “collagen”, a major structural protein " of the body. - flexible and can resist a lot of pulling force, so makes up ligaments (hold " bone to bone) and tendons (connect muscle to bone) - tissue with a lot of collagen is called “dense connective tissue which " appears whitish, so sometimes called white fiber

2. Elastic Fibers- made up of bundles of microscopic fibers embedded in " " “elastin” (protein) - elastic, but not as strong as collagenous fibers - easily stretched, but return to normal shape - common in body parts which stretch a lot ----->vocal cords/air passages " of respiratory system - appears yellowish, so called yellow fiber

3. Reticular Fibers- very thin, branched collagen fibers - help support many tissues

Connective Tissue Categories 1. “Loose Connective Tissue” (areolar tissue) " - form thin, delicate membranes in the body " - made of fibroblast cells that produce collagenous and elastin fibers " - bind skin to underlying organs " - makes up the space between muscle and skin

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- lies beneath epithelium layers

2. “Adipose Tissue” (fat) " - have cells which store fat droplets " - found beneath skin, between muscles, around kidneys for " protection, behind eyeballs, surface of heart, abdominal " " membranes, and some joints " - help cushion joints and organs " - insulate the body from heat loss

3. “Reticular Connective Tissue” " - a 3-D network of thin collagenous fibers containing WBCs " - supports the walls of liver, spleen and lymphatic organs

4. “Dense Connective Tissue” " - a lot of thick, closely packed collagenous fibers as well as a " " network of elastic fibers " - very strong " - binds body parts together making up tendons and ligaments " - also found in the dermis (inner skin layer) 5. “ Elastic Connective Tissue” " -made up of yellow elastic fibers " -found in the attachments between vertebrae of the spine and layers " of the walls of hollow internal organs, large arteries, parts of the " heart and airway membranes

*Specialized Types of Connective Tissue*

6. “Cartilage” " - very rigid to provide support and protection " - composed of cartilage cells called chondrocytes

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- 3 types differing by the type of intercellular material they have " a. Hyaline Cartilage- intercellular material of very fine " " " collagenous fibers " " - looks like white glass " " - found in ends of bones, soft part of nose " " - embryo skeletons begin as this type which gets " " replaced by bone " " - important in bone growth and repair of fractures " " b. Elastic Cartilage- intercellular material containing many " " " elastic fibers " " - more flexible than hyaline type " " - found in external ears and larynx (voice-box) " " c. Fibrocartilage- intercellular material of large collagenous " " " fibers " " - tough " " - make up vertebral disks of spine, bones of knee, and " " pelvic girdle " " - acts as shock absorber to cushion against pressure on " " above areas

7. “Bone” " - most rigid connective tissue " - hard due to mineral salts composed of calcium " - support the body " - protects vital organs (skull-brain; ribs-heart) " - a place for muscles to attatch " - contains red marrow to help produce blood cells " - composed of bone cells called osteocytes that form thin concentric " layers called lamellae 8. “Blood” " - made up of cells which are supported in an intercellular fluid called " blood plasma - include red blood cells (RBC), white blood cells (WBC) and " - platelets

*Muscle Tissue* p. 160 - composed of muscle fiber which is contractile, meaning they can contract " and relax (shorten and thicken, then elongate ) - 3 types: skeletal, smooth, and cardiac " 1. Skeletal Muscle - forms muscles that attach to bones and " " " " contract and relax under voluntary control " - composed of cells which are very long and narrow with " " alternating light and dark bands called striations " - important in moving body, writing, talking, chewing, etc.

2. Smooth Muscle - shorter than skeletal muscle " " - smooth because they donʼt have striations " " - contracts and relaxes under involuntary control " " - makes up many hollow organs: stomach, intestines, urinary " " bladder. uterus, and blood vessels

3. Cardiac Muscle- found only in the heart " " - cells are striated and joined end to end which causes a " " " branched and interconnected appearance " " - each cell has a single nucleus " " - there is a specialized area where one muscle cell touches " " another called an intercalated disk (page 161 fig. 5.30) " " - contracts and relaxes under involuntary control " " - pumps blood through the heart

*Nervous Tissue* - composed of nerve cells called neurons - found in the brain, spinal cord and peripheral nerves - help maintain homeostasis by coordinating and regulating many body " functions - assisted by neuroglia, which protect and supply nutrients to neurons ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

“ Membrane Types “ -when two or more different tissues work together to perform a specialized function they form an organ 1. Serous membrane = line body cavities that donʼt open to the outside " " (stomach, liver, heart) " - reduce friction between these organs and cavity walls by " " " secreting “serous fluid” which acts as a lubricant " - composed of a layer of simple squamous epithelium and " " " connective tissue

2. Mucous membrane = line the cavities and tubes which open to the " outside ( digestive tract, respiratory tract, reproductive and " urinary tracts) " - secrete “mucus” which protect the tissue it lines " - composed of epithelium tissue over a layer of connective tissue

3. Cutaneous membrane = largest organ in the body (skin) " - protects the body from harmful substances and helps regulate the " body temperature " - composed of stratified squamous epithelium, a lower layer of " " connective tissue, muscle and nervous tissue and adipose tissue

4. Synovial membrane = line the joints of the body " - produces “synovial fluid” which helps reduce abrasion at the joint " site ( knee joint - cracking knee ) " - composed entirely of connective tissue